1. Field of the Invention
The present invention relates to a ventilation device, and more particularly to a ventilation assembly mounted on the roof to expel heated air trapped under the roof.
2. Description of Related Art
When constructing low cost buildings, especially factories or warehouses, corrugated iron is used for outside walls and a roof. However, the corrugated iron absorbs and transmits solar radiation effectively causing heated air to build up and remain trapped inside the building that is causes temperature damage to the building, goods and people inside the building. Therefore, a ventilation device is required.
With reference to FIG. 4, a conventional ventilation device for a roof has multiple vents (62) each having an exhaust fan (61). The multiple vents (62) are formed on the roof of the building (60). The exhaust fans (61) are then mounted on the roof, corresponding to the vents (62) and rotating synchronously with the vents. Under normal conditions, heated air trapped under the roof rises and turns the exhaust fans (61) that causes the vents (62) to rotate and create an air flow through the building, (as shown by arrows), to maintain a constant temperature.
When a wind blows, the vents (62) rotate and cause the exhaust fans to rotate, thereby sucking the heated air out of the building. However, many of these conventional devices need to be put on a roof to work effectively and this raises construction costs. Also, the fans use moveable parts that need replacing or servicing, especially when built in high corrosive or harsh environment, such as near the sea in humid, high temperature regions.
In addition, some of conventional vents require electronic exhaust fans (61) to increase exhausting heated air from the roof. However, the conventional ventilation device has multiple electric exhaust fans and each electric exhaust fan is driven by external power source, the cost of radiating heat is not cheap.